Doing Physics, Second Edition: How Physicists Take Hold of the World

Doing Physics makes concepts of physics easier to grasp by relating them to everyday knowledge. Addressing some of the models and metaphors that physicists use to explain the physical world, Martin H. Krieger describes the conceptual world of physics by means of analogies to economics, anthropology, theater, carpentry, mechanisms such as clockworks, and machine

Overview

Doing Physics makes concepts of physics easier to grasp by relating them to everyday knowledge. Addressing some of the models and metaphors that physicists use to explain the physical world, Martin H. Krieger describes the conceptual world of physics by means of analogies to economics, anthropology, theater, carpentry, mechanisms such as clockworks, and machine tool design. The interaction of elementary particles or chemical species, for example, can be related to the theory of kinship—who can marry whom is like what can interact with what. Likewise, the description of physical situations in terms of interdependent particles and fields is analogous to the design of a factory with its division of labor among specialists. For the new edition, Krieger has revised the text and added a chapter on the role of mathematics and formal models in physics. Doing Physics will be of special interest to economists, political theorists, anthropologists, and sociologists as well as philosophers of science.

Editorial Reviews

"This is an important and provocative book, timely and full of insight. Fail to read it, and you may miss out on the physics of the future." —John Gribbin, New Scientist

Dick Easterlin

"Not many books about physics have six citations of Adam Smith. Building on the analogy that Nature is like an economic system, Krieger provides a novel analysis of how physicists construct models of the world. A fascinating insight into the way scientists think." —Dick Easterlin, University of Southern California

From the Publisher

Krieger... excellently tells those in our human society outside the physics world how physicists think, plan, and go about understanding nature.Choice

Isis

"An excellent [and innovative] book." —Isis

Choice

Krieger... excellently tells those in our human society outside the physics world how physicists think, plan, and go about understanding nature.Choice

New Scientist

"This is an important and provocative book, timely and full of insight. Fail to read it, and you may miss out on the physics of the future." —John Gribbin, New Scientist

 John Gribbin

Whole Earth Millennial Catalog

"This unusual book introduces 'the moves, the rituals, the incantations' physicists invoke as they go about conceptualizing Nature. The lucid-but-loaded writing makes quite complex ideas accessible to the mathless reader.... The rewards are a better understanding of how physics is done." —Whole Earth Millennial Catalog

How Physicists Take Hold of the World

Indiana University Press

Nature as a Factory; Handles and Stories. What Everyday Walls Must Do; Walls for a Factory; Walls as Providential. Particles, Objects, and Workers; What Particles Must Be Like; Intuitions of Walls and Particles. What Fields Must Be Like.

THE ARGUMENT IS: THE WORKINGS OF NATURE ARE ANALOGIZED to a factory with its division of labor. But here the laborers are of three sorts: walls, particles, and fields. Walls are in effect the possibility of shielding and separation; particles are the possibility of sources and localization; and fields allow for conservation laws and path dependence. Different kinds of degrees of freedom are associated with each type of laborer, and the laborers naturally restrict each other's degrees of freedom – if the Factory of Nature is to be as productive as it is. Corresponding to the efficiency of the division of labor in a factory or an economy is the comparative richness, elegance, economy, and wide applicability of a physical mechanism or theory or model. Technically, Maxwell's equations for electromagnetism are one realization of this political economy of a transcendental aesthetic, to honor both Adam Smith and Immanuel Kant in one phrase. (We discuss other mechanisms of production in subsequent chapters, for example ones in which exchange and the extent of the market are crucial features.) My claim is that physicists take Nature in this sense of manufacture; of course that sense being interpreted in terms of empirical "peculiarities," as Smith employs the term.

I

NATURE AS A FACTORY

Here is Adam Smith in the beginning of The Wealth of Nations (1776), describing the division of labor:

The greatest improvement in the productive powers of labor, and the greater part of the skill, dexterity, and judgment with which it is any where directed, or applied, seem to have been the effects of the division of labor....

But in the way in which this business [of pin making] is now carried on, not only the whole work is a peculiar trade, but it is divided into a number of branches, of which the greater part are likewise peculiar trades. One man draws out the wire, another straights it, a third cuts it, a fourth points it, a fifth grinds it at the top for receiving the head; to make the head requires two or three distinct operations; to put it on, is a peculiar business, to whiten the pins is another; it is even a trade by itself to put them into paper; and the important business of making a pin is, in this manner, divided into about eighteen distinct operations, which, in some manufactories, are all performed by distinct hands, though in others the same man will sometimes perform two or three of them....

This division of labour, from which so many advantages are derived, is not originally the effect of any human wisdom, which foresees and intends that general opulence to which it gives occasion. It is the necessary, though very slow and gradual, consequence of a certain propensity in human nature which has in view such extensive utility; the propensity to truck, barter, and exchange one thing for another....

As it is the power of exchanging that gives occasion to the division of labour, so the extent of this division must always be limited by the extent of that power, or, in other words, by the extent of the market. (Book 1, chapters 1–3)

The great invention here was to appreciate that in order to make pins or anything else, and to understand how they are made, one divides the work into specialized functions (those "peculiar trades"), attributes those abstracted functions to individual workers, and then provides for a system in which their labor is coordinated. Such an economy or a factory turns out to be both efficient and comprehensible. No individuals need do everything for their own livelihood, as they might on a farm. Nor would they need do everything to make a piece of equipment. What is needed is a mechanism to make sure that each individual knows what to do, and a means of organization and communication – whether it be a factory with its distinct tasks and processing lines, or a market economy with its specialized jobs, processes of exchange, and the prices attributed to labor and to goods. Such a division is not only efficient, it readily allows us to pinpoint what is going wrong if the factory does not function as we expect it to: some specialized task is not being done properly, or some particular means of coordination has become sticky. Rarely, if ever, is the whole factory to be reorganized. One almost always need merely to get hold of some specialized part and fix it.

Of course, it is a very great achievement to create such a factory or economy, to figure out a workable division of labor and a mechanism of production. Careful prior analysis may help, but often it is a matter of trial and error, and perhaps even of settling into a configuration that is not the best one, but at least it works – as David Hume (1779) would have suggested, a consequence of its having been until then "botched and bungled."

Now imagine that we, as economic anthropologists, were to come upon a seemingly productive system, and then tried to figure out how it worked. We may have some general ideas about how factories are organized and have some particular models or examples in mind. If the system just fits our ideas and templates, we are, so to speak, in business. But this particular system may be of a different shape and size, its boundaries uncertain or idiosyncratic. It is not quite so manifestly analogous to our models, not quite so readily gotten hold of with our regular toolkit – or so it seems. So we try out a tentative organization- and-flow chart drawn from our ideas, models, and tools, and see if it makes any sense of the workings of the factory. Along the way, we have to label the workers and work stations correctly, the product has to be distinguished from the garbage, the sections of the factory have to be delineated. Eventually, we might begin to understand how the factory works, why it is productive, and how it might break down and so exhibit new phenomena, and what to do to repair it if it does break down. (Recently, I have had this experience in an actual workshop, a small foundry.)

Such is the task, I would argue, that many physicists see themselves as taking on (as do many a theorist more generally) when encountering the world. Nature is in effect taken to be a factory or an economy. Can the physicist discern a division of labor within Nature, and a mode of organization, that makes sense of what Nature is doing – in that sense of a factory?

Soon after Smith, Immanuel Kant too provided a way of thinking of the division of labor required to make up Nature as physicists came to view it. The Transcendental Aesthetic that begins The Critique of Pure Reason (1781) might be taken as suggesting that space is just what is needed, grammatically and physically (what Kant called the "transcendental condition"), for objects to be separated and distinct from each other, and that time is the condition for there to be sequences of events and a causal relationship among them. Here, the natural division of labor in making up the world is between objects and space, between events and time. So we might ask: Which properties do we give to discrete objects, which to field-like space, and what mechanism do we prescribe for their interaction, so that we have an account of how the world works?

I take it that the physicist's initial problem is to discern "the political economy of the transcendental aesthetic": (1) to describe the precise modes or mechanisms by which objects are delineated and so separated from each other – the walls, shields, and surfaces; (2) the names or labels or properties through which objects have their own identity and are influential in the world – particles; and, (3) the provision and delineation of space with its own properties, so that in space's interaction with particles we have an account of Nature's workings – fields. As in a factory, the various laborers work together to produce Nature, according to rules which are often traditional and conventional – such as the rules that interaction between particles is "local" rather than "at a distance" and that neither particles nor fields have a memory of their past. Other divisions and rules are possible, but if the factory is to be productive the divisions and rules have to work together.

In my discussion, walls, particles, and fields are all taken to be laborers. Now, we might think it more natural to treat particles as most directly analogous to workers, and walls (and perhaps fields) as material and capital infrastructures much like the factory building and its machinery. But here I treat labor and capital as qualitatively similar inputs, so to speak, much as do economists in their formal production functions. I want to describe how they work together, deliberately avoiding any argument about particles vs. fields. As for the factory building (the mechanisms of interaction), we shall discuss its organization later in this chapter and in subsequent chapters.

In chapter 2 we describe the various kinds of individuals suitable for a factory or for an economy of Nature; in chapter 3 we delineate how exchange and the extent of the market define the factory; in chapter 4 we show how we set up both a factory and its outside suppliers so that the factory's production process is fairly straightforward; in chapter 5 we describe how an industrial engineer would investigate the factory's workings and the toolkit needed for making sense of such a factory; and in chapter 6, we describe some of the mathematical machinery in that factory and how scientists creatively use that machinery to do some of the work of physics.

Our first problem will be to describe the dynamics of the walls or shields, how things are kept apart or separated from each other so there could be space between them. Once we appreciate how walls are designed, then the design of particles and of fields follows in a natural way. But before trying to describe walls in some detail, I want to say a bit more about the task we are up to.

HANDLES AND STORIES

The attempt to make sense of Nature in terms of a division of labor may be thought of as participating in one of the abiding human endeavors: an attempt to articulate and analyze our experiences and the phenomena we encounter, in order to provide ourselves with a handle onto the world. Put differently, if we can manipulate the world we can understand it. Now the handles that will concern us here are the degrees of freedom – for example, position, temperature, charge, pressure, energy – of systems physicists concern themselves with. (The Preface provides an introductory discussion of the notion of degrees of freedom.) And those handles or degrees of freedom may be seen to be characteristic features of the laborers (walls, particles, fields) that make up the factory that produces Nature.

Our task here is to describe how physicists go about finding handles, setting up situations which are so to speak handleable, and how they view those handles as part of a coherent story or a theory of both manipulation and understanding. Such a description is perhaps much like the anthropological ethnographer's: What do these people (here, physicists and their community) do in their conceptual and practical work, what is the meaning for them of what they do, how does it make sense in their terms and in ours, and what kind of world or cosmology does it provide? As we shall see, what is striking in this kind of description is the obsessiveness and poignancy of people's commitments to their ways of going about their work. (On the use of such terms as obsessive and poignant, see the Preface.) No matter how difficult and peculiar it may seem to outsiders or even to themselves, their commitment to the practices and strategies is practically total. And the work, no matter how technical and purportedly arcane, may be seen in terms of tasks and motives we more generally share. Now, I should note that I am not talking here about the actual division of labor among scientists and others in the doing of science, about its social and bureaucratic character. Here the division of labor is that of Nature, namely, the divisions employed in physicists' conceptualizations.

Again, in this chapter we shall see how physicists are interpreting Nature as a factory; in the next, as a collection of parts that fit together; in the third, as a system of interrelationship and interaction and exchange, much like Smith's economy or in kinship and marriage; in the fourth, as a theatrical stage that displays an abstracted if everyday world, the motivating problem being how something arises from nothing; in the fifth chapter, how physicists interpret Nature as something to be handled and poked and so observed and changed; and, in the sixth chapter we describe how mathematics provides a supple language and a machinery physicists create and employ for modeling and understanding Nature. In sum, these physicists go about inventing a division of labor for Nature, one in which things are made up of other things, in which everything that is not forbidden is allowed, where whatever happens happens on an empty stage, where we find out about the world by poking at it, and we learn to talk about the world, in a variety of dialects, using mathematical machinery.

II

WHAT EVERY DAY WALLS MUST DO

A wall creates two sides, an inside and an outside, a left side and a right side, a core and a periphery, a black box and an external world, a body and an environment. Walls divide the world into separate rooms, or discrete particles, or isolated and enclosed and demographically-addable individuals – perhaps with space between them. Now, much of physical science is a story of individuals in interaction, whether it be interactions of atoms in chemistry or of elementary particles in physics. Physicists often then take as their task the creation (or invention or discovery, as you will) of just the right kind of walls, with just the right possibility for being breached, so that there may be the right kind of interacting individuals so as to manufacture Nature. So, walls in thermodynamics may define suitably restricted systems which then, say, have definite temperatures, those walls perhaps breached by heat or material. Or, the valence cloud of an atom's outer electrons, participating in the chemical bond and so acting as a wall, in effect hides the chemically uninteresting features of an atom or molecule – they are too tightly bound to interact – and yet allows for a breach of energy or charge at the meeting place of the atom and the world of other atoms around it.

Now there is no single canonical definition of what a wall must be like. Rather, there are a variety of archetypal cases and conventional analogies that instantiate what a wall must do and just how it does that walling-off. Some of these notions of walls will seem peculiar and strange. But it is just that strangeness we feel that tells us that this is a conceptual and practical invention, deriving from a set of experiences and necessities we ourselves may not have had – but could have. I want to look at the kinds of walls – the kinds of conceptions of walls – that physicists need to do their work, to analyze the production of Nature. ("What kinds of walls does Nature need?" is perhaps an allowable concision.) For purposes of exposition I place ourselves ("we") in the role of a physicist.

Everyday walls may be defined as boundaries, interfaces, functions, skins, and dynamical processes. Boundaries delineate separation, interfaces describe permeability and interdigitation, functions allow for specific conditions to be maintained at the wall, skins hold together and bind, and dynamical processes respond to the outside world.

The wall may be a boundary line, like that between nations. Such a boundary might also allow for interchanges of specific goods in specific directions, and it might maintain certain conditions on itself (of purity or of temperature, for example). The boundary line and its conditions would seem to have to be maintained actively, by border guards, so to speak, if the boundary is not to fall apart. Yet, still, for many analytic purposes we need merely specify the spatial separation that the boundary defines (or its topology) and its exact shape.

Meet the Author

Martin H. Krieger, who was trained as a physicist at Columbia University, has been a Fellow at the Center for Advanced Study in the Behavioral Sciences and at the National Humanities Center. He is author of Marginalism and Discontinuity: Tools for the Crafts of Knowledge and Decision (1989), Constitutions of Matter: Mathematically Modeling the Most Everyday of Physical Phenomena (1996), and Doing Mathematics: Convention, Subject, Calculation, Analogy (2003). He is on the faculty of the University of Southern California, and has taught at Berkeley, Minnesota, MIT, and Michigan.